With dwindling petroleum resources, fluctuating energy prices, and environmental concerns, the development of energy efficient biorefinery processes to produce biobased chemicals from renewable, low cost, carbon resources offers a unique solution to overcoming the increasing limitations of petroleum-based chemicals.
One chemical class that has many industrial uses and could be manufactured using a biorefinery process is acrylates such as acrylic acid and acrylic acid esters. The market demand for these chemicals is estimated to be nearly 4 Million Metric Tons/yr, roughly split between acrylic acid and acrylate esters. The total market size for this chemical is on the order of $11 billion/yr with annual projected growth rates of about 4%. The growth is being driven by emerging consumer markets in China and India that use acrylic acid as an intermediate in products such as personal care (diapers, hygiene pads), detergents, flocculants, polymers, coatings, adhesives and sealants.
Currently, the commercial production of petroleum-based acrylic acid is carried out via a two stage process whereby propene (a byproduct of ethylene/gasoline production) is partially oxidized in air. Renewable routes to acrylate production are also in development and include such processes as the direct production of acrylic acid from fermentation of genetically engineered microbes, production of small molecule intermediates from genetically engineered microbes such as glycerol, lactic acid, crotonic acid and 3-hydroxypropionate which are then chemically converted to acrylic acid or the production of polymeric intermediates such as polyhydroxypropionate (PHA) by genetically engineered microbes which when heated to a high temperature produce acrylic acid. The pyrolysis of biologically produced PHA polymers is a particularly advantageous route for obtaining acrylic acid and its esters as it avoids the problems of low product yield and cell toxicity associated with generating small molecule chemicals directly in the microbes. However, the process should additionally minimize the production of impurities that are generated during pyrolysis of the PHA biomass and that are recovered along with the acrylic acid.
A need therefore exists to develop biorefinery processes for manufacturing acrylic acid that address not only improvements in the yield, purity, and cost of the chemical but also uses sustainable starting materials having a more positive impact on the environment.